I found the place (sorry, it’s in French, so I’m not sure about the translation Hostname / Device Name).
It’s also in Sharing (Settings -> Sharing -> Device Name).
The problem is I can’t find how to unlock it. (I think as an admin it’s unlocked by default.)
When I want to add a printer, the way to unlock it is very clear.
In Settings -> System -> Date and time, there is an unlock button, but a little bit different than in Settings -> Printers.
I don’t find what are the corresponding settings:
In Settings -> Keyboard, I’m able to add a keyboard without admin password.
In Settings -> Network/WiFi/Bluetooth, all network settings I know are allowed to be changed without admin password.
What’s the difference? Settings -> Sharing -> Device Name and Settings -> System -> About -> Device Name seem to point on the same thing.
Anyway, there is no unlock button at all, which is the most annoying thing.
I like the ergonomics of macOS, I find it simpler.
There is an unlock button which is always shown, and which is only disabled when no setting requires it. It’s also quite unobtrusive, more like Settings -> System -> Date and time than Settings -> Printers or Settings -> System -> Users.